Search for supersymmetry via resonant final states with the ATLAS detector

1. Search for supersymmetry via resonant final states with the ATLAS detector Adrien Renaud (LAL-Orsay IN2P3/CNRS and Université Paris-Sud) for the Atlas collaboration. HEP2012 – Valparaiso, Chile January 6, 2012 • PRL (arXiv:1103.5559) • EPJC (arXiv:1109.3089) • EPJCL (arXiv:1110.2693)

2. Overview • Introduction • RPV tau sneutrino search in the eμ final state • 3) Scalar gluon search in the four jets final state • 4) Conclusion

3. Susy via Resonances ?? • MSSM: • particles with L or B numbers • - renormalizable terms violate L or B Potential disaster: - much too fast proton decay No resonances --> look for an excess in SM tail • RP conservation: • - PR= (-1)2S • (-1)3(B-L) • forbids L and B violating terms • PR= +1 (-1) for SM (SUSY) particles • LSP stable, in all cascade decays, DM

4. Susy via Resonances ?? RP violated susy: -- B and L conservation ? neutrino masses and mixing ? … -- some of the couplings have to be small --> stable proton Beyond MSSM with RP conservation: Extended supersymmetry: -- minimal ? new pheno ? flavor-violation ? dirac gauginos ? … -- new particles with PR= +1 --> resonances in RP conserved susy ! --> Scalar-gluon search --> RPV tau sneutrino search

5. Introduction to RPV Sneutrino search Search for RPV sneutrino with lepton number violation decay: λ’311 ≠ 0 and λ312 ≠ 0 • - eμ clean signature with low SM background • previous limit from low energy tau branching ratio: • λ’311 < 0.11 and λ312 < 0.07 for Mslepton= Msquark= 100 GeV

6. Event Selection Using L=1.07 fb-1: 2011 data Single lepton (e, μ) trigger (100±1%) Signal generated with HERWIG + JIMMY + NLO k-factor Electron: -- pT > 25 GeV -- |η| < 1.37 or 1.42 < |η| < 2.47 -- isolated in EM calorimeter -- shower shape requirements Muon: -- pT > 25 GeV -- |η| < 2.4 -- reconstructed in ID and MS -- isolated in the ID - Exactly one muon and one electron with opposite-sign charge - No requirements on #jets and ETmiss

7. Highest invariant mass (662 GeV) eμ event

8. Backgrounds Physics backgrounds (real leptons) -- Z/γ*->tau,tautop pairsingle topWW, WZ, ZZ -- Estimated using MC corrected for data/MC differences Instrumental background (lepton faked by photon or jet) -- W/Z+γ estimated using MC -- SM multijet and W/Z+jets estimated using data-driven matrix method: 1) Define loose and tight lepton definitions 2) Apply on all events to get NTT,NTL,NLT,NLL 3) Determine efficiency (r) and fake rate (f) for a lepton that has passed the loose definition to also pass the tight definition 4) Solve the 4*4 matrix:

9. Data / Background Final observable: Kolmogorov-Smirnov test probability: 56% Data consistent with absence of new physics

10. Limits Bayesian method(uniform prior for signal cross section): Excluded @ 95% CL: - 135 fb @ 100 GeV - 4.5 fb @ 1 TeV Best limits for: - Msneutrino > 270 GeV Excluded @ 95% CL: - 1.32 TeV for λ′311 = 0.10 and λ312 = 0.05 - 1.45 TeV for λ′311 = 0.11 and λ312 = 0.07

11. Introduction to scalar-gluon search Wojciech Kotlarski@7TeV Pair production Single production A 4-jets final state: Sgluon = Scalar color-octet with SM-like PR • Non minimal realisations of SUSY: • Extended SUSY: hybrid N=1/N=2 • Extended R-Parity: MRSSM Production: Decay: Diff cross section from PL.B672,2009 implemented as external process to PYTHIA

12. Analysis strategy Using L=34 pb-1: 2010 data Multijet trigger: 4 jets pT> 55 GeV --> Low threshold = low mass ~same amount recorded in 2011 for this threshold Scalar production at rest suppressed by factor β -- > “ Slightly Boosted ” regime Combinatory: Event selection: • 4 jets pT > 0.55 * Msgluon • ΔRjj < 1.6 • |Cos(θ*)| < 0.5 • |M1–M2|/(M1+M2) < 0.075 Minimize : | ΔRij – 1 | + |ΔRkl - 1| Whereijkl are the 4 leading jets Look for an excess in the (M1+M2)/2 distribution.

13. Multijet Event

14. DATA-driven BGR estimation Only Simulation Background Background estimation Signal Background + Signal JHEP09(2011)074 • ABCD method: • NA = NB * NC / ND • Take shapeof final observable • in region B via a fit: 0.50.7 C D |M1–M2|/(M1+M2) 7.5% A B |Cos(θ*)|

15. ABCD results (1/2) Agreement between data and background prediction: Good agreement A/B Prediction within 1-2 sigma stat Reasonably good fit

16. ABCD results (2/2) Systematic uncertainties

17. Limits Profile likelihood ratio and CLSapproach : Likelihood is the Product of : -- Poisson for each bin (shape analysis) -- Gaussian for each systematic uncertainty • Contamination in ABCD method. • Correlations between systematic. L = 34 pb-1: Excluded σ@ 95% CL : 1 nb @ 100 GeV 200 bp @ 200 GeV • Excluded @ 95% CL: • Sgluon : 100-185 GeV (except 5 GeV around 140 GeV)

18. Conclusion Λ’’313 q q Search for tau sneutrino decaying to eμ: -- limits for sneutrino mass vs coupling in RPV (0.1 – 2. TeV) Search for pair-produced sgluon decaying to four-jets: -- limits for low mass colored scalar (100 – 200 GeV)  Already 3 published papers  Other interpretations already available (LFV Z’, hypercolor). More to come with higher Luminosity, Energy, refined analysis Funny link between 2 analysis: - slightly modified analysis to search for RPV stops !

19. Spare

20. The ATLAS detector

21. Jet reconstruction JER Jets : -- Anti-ktR=0.6 -- EM+JES calibration -- pT > 20 GeV && |η| < 2.8 JES

22. RPV sneutrino search ETmiss not used in the analysis to make the search more generic

23. Other interpretations Z′ gauge bosons with lepton flavor violating (LFV) interactions --> Same analysis as for stau sneutrino Hypercolor model: Hyperpion, scalar color octet --> Same as analysis as sgluon

24. Data / MC (1/2) ALPGEN+HERWIG+JIMMY SM-multijet production 1) 4 jets pT > 0.55 * Msgluon --> sliding cut 2)ΔR(jj) < 1.6 after pTcut (4 jets pT>55 GeV -> M=100GeV)

25. Data/MC (2/2) 3)|M1–M2|/(M1+M2) < 0.075 After pT cut and ΔR cuts 4)|Cos(θ*)| < 0.5 After all cuts but cos(θ*) - Reasonably good description - Ratio compatible with 1 even without JES uncertainty - large MC stat uncertainty

26. Data / Background Good agreement with SM prediction